Flotation machine

ABSTRACT

A flotation machine for recovering valuables or concentrates from a raw material, which comprises: a flotation cell having at least one froth-discharging opening located at the lower part of a side wall of said cell; an agitating means fitted within the central part of said cell; and at least one froth-discharging pipe fixed within said cell, the one end opening of said pipe being connected with said froth-discharging opening of said cell and the other end opening of said pipe being held at a level lower than the upper end of said side wall but higher than the surface level of the pulp or liquid charged to be subjected to flotation, thereby forming at least one froth-discharging passage within said cell.

United States Patent [1 1 Nagahama [541 FLOTATION MAClllNE [75] inventor: Tatsuya Nagahama, Tokyo, Japan [73] Assignee: Mitsui Mining & Smelting Co., Ltd.,

Tokyo, Japan [22 Filed: Sept. 8, 1972 211 Appl.No.: 287,269

[30] Foreign Application Priority Data Sept. 14, 1971 Japan 46-71605 [52] US. Cl. 210/221, 209/169 [51] Int. Cl B03d 1/24 [58] Field of Search 209/162, 164-166,

[56] References Cited Apr. 9,1974

OTHER PU BLlCATlONS Denver Sub A" Flotation, Denver Equipment Co., Bulletin No. F10. B29, 8/5/49, pages 10-13.

Primary Examiner-John Adee As'sislant Examiner-Robert H. Spitzer Attorney, Agent, or Firm-Woodhams, Blanchard and Flynn [5 7] ABSTRACT A flotation machine for recovering valuables or concentrates from a raw material, which comprises: a flotation cell having at least one froth-discharging opening located at the lower part of a side wall of said cell; an agitating means fitted within the centralpart of said cell; and at least one froth-discharging pipe fixed within said cell, the one end opening of said pipe being connected with said froth-discharging opening of said cell and the other end opening of said pipe being held at a level lower than the upper end of said side wall but higher than the surface level of the pulp or liquid charged to be subjected to flotation, thereby forming at least one froth-discharging passage within said cell.

8 Claims, 7 Drawing Figures FLOTATION MACHINE BACKGROUND OF THE INVENTION a. Field of the Invention The present invention relates to a flotation machine for the purpose of recovering valuables or concentrates through flotation of ores or recovering ions contained in a liquid or recovering particles contained in a liquid resulting from reaction between said ions and a reagent applied upon concentrating them by flotation.

b. Description of the Prior Art The conventional flotation machines are mostly of such structure as shown in FIG. 1 of the appended drawings. In said FIG. 1, the numeral reference 1 denotes the impeller shaft connected with the impeller (which is not shown herein), denotes the flotation cell, and 6 denotes the trough for discharging the froth 9 (i.e., the aggregate of bubbles whereon minerals, ions or solid particles resulting from reaction between the ions and a reagent are adhering). In the operation of,

the so-called mechanically agitated flotation machine of such construction as above, agitation-of the ore pulp or liquid and mixing of the air are simultaneously performed, and as a result, the bubbles generated in the pulp or liquid come up to the surface of the pulp or liquid within the flotation machine andto said bubbles are adhered minerals, ions, or solid particles resulting from reaction between said ions and a reagent, to thereby form a froth. This froth is discharged into the frothdischarging trough through the froth-discharging discharging opening provided on a portion wall at the surrounding of the upper end of the flotation machine. In this way of discharging the froth, however, the froth formed in the vicinity of the froth-discharging opening or the froth-discharging trough is apt to be discharged faster than the froth formed in the other parts. In other words, the froth formed in a part distant from the frothdischarging opening tends to stay for a long time on the surface of the pulp or liquid before it is discharged. As a result, a part of the bubbles within the froth disappear and the suspended matter once floated off the pulp or liquid is put back in the pulp or liquid again, causing the flotation efficiency to decrease.

There is known another type of flotation machine. It is the so-called pneumatic flotation machine which is devised to perform agitation of the pulp or liquid and mixing of the air simultaneouslyby introducing compressed air without employing an impeller an in the above mechanically agitated flotation machine. There is also known a flotation machine which. combines theforegoing' mechanically agitated flotation'machine and the pneumatic flotation machine. Even flotation machines of these types, however, have failed. to avoid the decrease in flotation efficiency ascribable to a prolonged stay of the froth on the surface of the pulp or liquid as set forth in the foregoing. I

SUMMARY OF THE INVENTION The object of the present invention is to provide an improved flotation machine which renders it possible to discharge the froth formed on the surface of the pulp or liquid in a very short time.

The present invention features the provision of at least one hollow cylinder or froth-discharging pipe for the above flotation machine for the purpose of rapidly discharging the froth to the outside of the machine.

According to the present invention, it is essential to dispose said hollow cylinder (froth-discharging pipe) within the flotation machine so that the upper end opening of said hollow cylinder is held at a level higher than the surface level of the pulp or liquid to some degree so that the froth formed on the surface of the pulp or liquid may continuously flow into said upper end opening. According to the present invention, it is desirable to hold the upper end opening of said hollow cylinder at a position 1 50 cm higher than the surface level of the pulp or liquid charged into the flotation machine for flotation. In this way, it is possible to prevent the pulp or liquid being subjected to flotation from flowing directly into the hollow cylinder and from being discharged to the outside of the flotation machine.

The lower end opening of the hollow cylinder is connected with a froth-discharging opening located at an appropriate place in the lower part of a side wall of the flotation cell. By virtue of the provision of the hollow cylinder within the flotation machine in this way, the froth flowing into the upper end opening of the hollow cylinder runs down through the hollow cylinder and is continuously discharged to the outside of the flotation machine through the froth-discharging opening. Therefore, when the upper end opening of the hollow cylinder for froth-discharging purpose as above, the froth is prevented from staying for a long time after having been formed on the surface of the pulp or liquid, and is rapidly discharged to the outside of the flotation machine.

BRIEF DESCRIPTION OF THE DRAWINGS The preferred embodiments of the flotation machine according to the present invention will be discussed more concretely in the following by reference to the accompanying drawings. In the accompanying drawings,

FIG. 1 is a perspective view of a prior art mechanically agitated flotation machine.

FIG. 2 is a perspective view of an embodiment of a mechanically agitated flotation machine according to thepresent invention.

FIG. 3 is a central sectional view of the flotation machine of FIG. 2.

FIG. 4 is a perspective view of another embodiment of a mechanically agitated flotation machine according to the present invention.

FIG. 5 is a central sectional view of the flotation machine of FIG. 4.

FIG. 6 is a plan view of the flotation machine of FIG. 4.

FIG. 7 is a plan view of still another embodiment of the mechanically agitated flotation machine according to the present invention.

Referring to FIG. 2 and FIG. 3, the numeral reference ll denotes the impeller shaft, 12 denotes the stand pipe (which constitutes the hollow cylinder for air-blowing purpose and the inner wall of the hollow cylinder for froth-discharging purpose), l3 denotes the impeller, 14 denotes the guide vane (or stabilizer), 15 denotes the flotation cell, 16 denotes the frothdischarging trough, 17 denotes the hollow cylinder for froth-discharging purpose, and 18 denotes the coupling pipe to interconnect the froth-discharging opening 18 and said hollow cylinder. The flotation machine of the present invention as illustrated by FIG. 2 and FIG. 3

consists of a conventional flotation machine combined with the froth-discharging hollow cylinder 17 and the coupling pipe 18 provided therefor. When the flotation is effected by employing such a flotation machine of the present invention as above, the air is drawn into the flotation machine through the opening between the impeller shaft 11 and the stand pipe 12 by virtue of the rotation of the impeller 13, and the froth formed thereby flows in the direction of the arrow 19 to be discharged rapidly through both the froth-discharging trough l6 and the froth-discharging hollow cylinder 17.

As to the shape of the froth-discharging hollow cylinder l7 applicable to the present invention, a cylindrical tube is most convenient for shaping, but other shapes such as triangular tube, a square tube and a polygonal tube are also applicable. As the material for the frothdischarging hollow cylinder, the known materials for the conventional flotation machine, such as carbon steel, stainless steel, synthetic resin, etc., can be employed at ones discretion. Besides, it will do to make the fixed elevation of the upper end opening of the froth-discharging hollow cylinder adjustable in the vertical direction to thereby make it possible to modify optionally the rate of froth discharge to the frothdischarging trough and to the froth-discharging hollow cylinder according to the condition of flotation. And, the ratio of the total surface area of the upper and opening of the froth-discharging hollow cylinder to the surface area of the froth-forming zone may be modified optionally according to the condition of flotation. But, according to the present invention, it is preferable to adjust the ratio of the total surface area of the upper end opening of said hollow cylinder to the surface area of the froth-forming zone of the flotation cell to be in the range of from l/l to II].

FIGS. 4 through 6 show a flotation machine wherein the froth-discharging hollow cylinder is installed in a cylindrical flotation cell instead of a square flotation cell such as shown in FIG. 2 and FIG. 3. In this figure, there is provided an upper froth-deflecting guide vane 20, an impeller shaft 21, a stand pipe 22, an impeller 23, lower guide vanes 24, a flotation cell wall 25, a froth discharging trough 26, a hollow cylinder 27 for froth discharging purposes, and a coupling pipe 28 to connect said cylinder 27 to froth-discharging opening 28. The arrow 29 indicates the direction of flow to the froth. Especially, this is a flotation machine devised to guide and impart movement to the layer of froth. Accordingly, when the froth-deflecting guide vane 20 is further installed in it as shown in FIG. 4, inasmuch as the surface level of the layer of froth on the occasion of its rotation in the direction shown in FIG. 6 (that is, in the direction of the arrow) is lowered toward the center of the flotation machine, the interception of this motion of the froth layer by means of the vane 20 consisting of a curved plate as shown in the drawings makes the froth move toward the low-level center, that is, the upper end opening of the hollow cylinder 27, thereby increasing the thickness of the layer of froth thereat and rendering it possible to recover a lot of froth into the froth-discharging hollow cylinder 27, said froth containing but a trifling portion of the underlying pulp or liquid. Such being the case, it is advisable to install said hollow cylinder in combination with the froth deflecting vane.

On the occasion of performing ion flotation for the purpose of recovering metal ions contained in the waste water in extremely small quantities, it is necessary to discharge plenty of froth rapidly as said froth is apt to disappear, and, from this point of view, application of the flotation machine according to the present invention is very effective.

FIG. 7 is the plan view of a mechanically agitated flotation machine as devised to guide and impart movement to the froth layer and this machine is equipped with the froth-deflecting vane 40, FIG. 7 illustrates the location of said froth deflecting vane 40 and the direction of its curvature. In other words, in case the froth is made to rotate in the direction of the arrow, it can be discharged through the center of the machine exclusively, not through the surrounding wall thereof. According to the present invention, therefore, the outer froth-discharging trough is not always required; the discharge of the froth can be sufficiently effected by enlarging the diameter of the froth-discharging hollow cylinder. In this connection, referring to FIG. 7, the froth-deflective vane 40 is of the same shape as the froth-deflective vane 20 in FIG. 4 excepting that it is convex in the direction of the rotation of the froth, the two ends of said vane being fixed on the inner wall of the flotation cell 35 and the outer wall of the frothdischarging hollow cylinder 37 respectively. The numeral reference 31 denotes the impeller shaft, 32 denotes the stand pipe and arrow 39 denotes the direction in which the froth is discharged.

The above described flotation machines according to the present invention are of such construction that a double-wall froth-discharging hollow cylinder is fitted on an impeller shaft.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereunder will be given a few examples of the flotation tests to clarify the difference of the effect between the flotation performed by employing the flotation machine according to the present invention and that performed by employing the conventional flotation machine.

TEST 1 Flotation of zinc ores was conducted by employing a flotation machine according to the present invention, such as shown in FIG. 4 and FIG. 5 (said flotation machine being l,675 mm in the inside diameter of the flotation cell, 1,000 mm in height, 500 mm in the inside diameter of the froth-discharging hollow cylinder and 200 mm in the inside diameter of the stand pipe).

Meanwhile, flotation of zinc ores was conducted by employing a conventional flotation machine obtained by removing the froth-discharging hollow cylinder from the above flotation machine for the purpose of comparison.

The conditions of flotation in both cases were as follows, and the results of flotation conducted by the use of said two machines were as shown in the following Table 1 respectively.

ore: grade in zinc 4 wt%, -mesh sieve passable content wt% concentration of pulp: 40%

kind and concentration of reagent applied: copper sulfate I20 g/t, sodium ethyl xanthate 20 g/t, frother 40 g/t time of flotation: 5 minutes TABLE 1 Performance Grade in Yield Zn in of Flotafloating Zn Remarks tion machine ore flotation machine Froth was discharged under the present 34.0 95 through both the frothinvention discharging hollow cylinder and the frothdischarging trough at the rate of about I :l. comparative flo- Froth was discharged tation machine 34.5 88 through the frothdischarging trough exclusively TEST 2 kind and concentration V of reagent applied sodium sulfide 18 mg/l sodium ethyl xanthate mg/l flocculant 0.02 mg/l frother 2 mg/l time of flotation: 10 minutes TABLE 2 Performance Concentration of Cu ion residual Cu removal Flotain postrate Remarks tion machine flotation Froth was discharged through both the froth-discharging hollow cylinder and waste water flotation machine e froth-discharged trough at the rate of about 2:1. under the present 0.3 99 invention comparative Froth was discharged through the froth-discharging trough exclusively. flotation machine 6.0 80

As is evident from the results of the above two tests, the flotation efficiency of the flotation machine according to the present invention is by far superior to that of the comparative flotation machine.

What is claimed is:

l. A flotation machine, comprising;

a flotation cell having an upright side wall, said side wall having a froth-discharging opening located close to the lower end thereof,

double-walled hollow cylinder disposed within the central portion of said cell and extending downwardly therein to a position close to the bottom of said cell, said cylinder being defined by an upright inner wall and an upright outer wall encircling and spaced outwardly from said inner wall and defining therewith a passage through which froth can flow downwardly, the bottom end of said passage being closed and the upper end of the passage being open so that froth can flow into said passage at the upper end thereof, the upper end of said outer wall being located at a position below the upper end of the side wall of the cell and higher than the upper surface of the liquid substance subjected to flotation in the cell;

pipe connecting said froth-discharging opening to the lower end of said passage for discharging, by gravity, downwardly flowing froth from said passage through said froth-discharging opening;

and agitating means disposed below said cylinder for agitating the contents of said cell.

2. A flotation machine according to claim 1, in which said inner wall extends above the upper end of said outer wall.

3. A flotation machine according to claim 1, in which said agitating means comprises an upright rotatable impeller shaft extending inside of and being spaced from said inner wall, and an impeller secured to the lower end of said shaft and disposed directly below the bottom of said cylinder.

4. A flotation machine according to claim 3, in which a froth deflecting vane extends between said side wall of said cell and the upper end of said outer wall of said hollow cylinder for deflecting froth into the upper end of said passage.

5. A flotation machine according to claim 4, including a froth discharging trough attached to the upper end of said side wall of said cell.

6. A flotation machine according to claim 1, including a froth-discharging trough attached to the upper end of said side wall of said cell.

7. A flotation machine according to claim 1, in which the bottom end of said passage is closed by an imperforate bottom wall which extends transversely between the lower ends of said inner and outer walls.

8. A flotation machine according to claim 7, in which said bottom wall slopes downwardly in a direction from said inner wall toward saidouter wall, and said pipe is connected to and slopes downwardly away from the lower end of said outer wall. 

1. A flotation machine, comprising; a flotation cell having an upright side wall, said side wall having a froth-discharging opening located close to the lower end thereof, a double-walled hollow cylinder disposed within the central portion of said cell and extending downwardly therein to a position close to the bottom of said cell, said cylinder being defined by an upright inner wall and an upright outer wall encircling and spaced outwardly from said inner wall and defining therewith a passage through which froth can flow downwardly, the bottom end of said passage being closed and the upper end of the passage being open so that froth can flow into said passage at the upper end thereof, the upper end of said outer wall being located at a position below the upper end of the side wall of the cell and higher than the upper surface of the liquid substance subjected to flotation in the cell; a pipe connecting said froth-discharging opening to the lower end of said passage for discharging, by gravity, downwardly flowing froth from said passage through said froth-discharging opening; and agitating means disposed below said cylinder for agitating the contents of said cell.
 2. A flotation machine according to claim 1, in which said inner wall extends above the upper end of said outer wall.
 3. A flotation machine according to claim 1, in which said agitating means comprises an upright rotatable impeller shaft extending inside of and being spaced from said inner wall, and an impeller secured to the lower end of said shaft and disposed directly below the bottom of said cylinder.
 4. A flotation machine according to claim 3, in which a froth deflecting vane extends between said side wall of said cell and the upper end of said outer wall of said hollow cylinder for deflecting froth into the upper end of said passage.
 5. A flotation machine according to claim 4, including a froth-discharging trough attached to the upper end of said side wall of said cell.
 6. A flotation machine according to claim 1, including a froth discharging trough attached to the upper end of said side wall of said cell.
 7. A flotation machine according to claim 1, in which the bottom end of said passage is closed by an imperforate bottom wall which extends transversely between the lower ends of said inner and outer walls.
 8. A flotation machine according to claim 7, in which said bottom wall slopes downwardly in a direction from said inner wall toward said outer wall, and said pipe is connected to and slopes downwardly away from the lower end of said outer wall. 